Ground-Fault Protection - ABB REM 610 Technical Reference Manual

1MRS755537
5.1.4.6.
Motor Protection Relay
Technical Reference Manual - ANSI Version
It is possible to block the tripping of the undercurrent element by applying a digital
input signal to the relay.
Element 37 can be set out of operation in SGF3. This state will be indicated by
dashes on the LCD and by "999" when the set pickup value is read via serial
communication.
When element 37 picks up during motor start up, no pickup signal will
be generated.

Ground-fault protection

The non-directional ground-fault current protection detects phase-to-ground
currents, caused by ageing and thermal cycling, for instance.
When the ground-fault current exceeds the set pickup value of element 51N, the
element will generate a pickup signal after a ~ 50 ms' pickup time. When the set
operate time at definite-time characteristic elapses, the element will generate a trip
signal. The element can be given an instantaneous characteristic by setting the
operate time to the minimum, i.e. 0.05 s. The ground-fault element will be reset in
50 ms after the ground-fault current has fallen below the set pickup value of the
element.
It is possible to block the tripping of the ground-fault element by applying a digital
input signal to the relay.
Element 51N can be set out of operation in SGF3. This state will be indicated by
dashes on the LCD and by "999" when the set pickup value is read via serial
communication.
To prevent the contactor in a contactor controlled drive from operating at too high
phase currents, the ground-fault element can be set to be disabled when one or
several phase currents exceed the FLA of the motor four, six or eightfold. The
selection is made in SGF4.
When element 51N picks up during motor start up, no pickup signal
will be generated.
The FLA secondary does not affect the ground fault current, I
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